var settings = {
  particles: {
    length: 500, // maximum amount of particles
    duration: 2, // particle duration in sec
    velocity: 100, // particle velocity in pixels/sec
    effect: -0.75, // play with this for a nice effect
    size: 30, // particle size in pixels
  },
};
(function () {
  var b = 0;
  var c = ['ms', 'moz', 'webkit', 'o'];
  for (var a = 0; a < c.length && !window.requestAnimationFrame; ++a) {
    window.requestAnimationFrame = window[c[a] + 'RequestAnimationFrame'];
    window.cancelAnimationFrame =
      window[c[a] + 'CancelAnimationFrame'] ||
      window[c[a] + 'CancelRequestAnimationFrame'];
  }
  if (!window.requestAnimationFrame) {
    window.requestAnimationFrame = function (h, e) {
      var d = new Date().getTime();
      var f = Math.max(0, 16 - (d - b));
      var g = window.setTimeout(function () {
        h(d + f);
      }, f);
      b = d + f;
      return g;
    };
  }
  if (!window.cancelAnimationFrame) {
    window.cancelAnimationFrame = function (d) {
      clearTimeout(d);
    };
  }
})();
var Point = (function () {
  function Point(x, y) {
    this.x = typeof x !== 'undefined' ? x : 0;
    this.y = typeof y !== 'undefined' ? y : 0;
  }
  Point.prototype.clone = function () {
    return new Point(this.x, this.y);
  };
  Point.prototype.length = function (length) {
    if (typeof length == 'undefined')
      return Math.sqrt(this.x * this.x + this.y * this.y);
    this.normalize();
    this.x *= length;
    this.y *= length;
    return this;
  };

  Point.prototype.normalize = function () {
    var length = this.length();
    this.x /= length;
    this.y /= length;
    return this;
  };
  return Point;
})();

var Particle = (function () {
  function Particle() {
    this.position = new Point();
    this.velocity = new Point();
    this.acceleration = new Point();
    this.age = 0;
  }
  Particle.prototype.initialize = function (x, y, dx, dy) {
    this.position.x = x;
    this.position.y = y;
    this.velocity.x = dx;
    this.velocity.y = dy;
    this.acceleration.x = dx * settings.particles.effect;
    this.acceleration.y = dy * settings.particles.effect;
    this.age = 0;
  };
  Particle.prototype.update = function (deltaTime) {
    this.position.x += this.velocity.x * deltaTime;
    this.position.y += this.velocity.y * deltaTime;
    this.velocity.x += this.acceleration.x * deltaTime;
    this.velocity.y += this.acceleration.y * deltaTime;
    this.age += deltaTime;
  };

  Particle.prototype.draw = function (context, image) {
    function ease(t) {
      return --t * t * t + 1;
    }
    var size = image.width * ease(this.age / settings.particles.duration);
    context.globalAlpha = 1 - this.age / settings.particles.duration;
    context.drawImage(
      image,
      this.position.x - size / 2,
      this.position.y - size / 2,
      size,
      size
    );
  };
  return Particle;
})();
/*

  * ParticlePool class

  */
var ParticlePool = (function () {
  var particles,
    firstActive = 0,
    firstFree = 0,
    duration = settings.particles.duration;
  function ParticlePool(length) {
    // create and populate particle pool
    particles = new Array(length);
    for (var i = 0; i < particles.length; i++) particles[i] = new Particle();
  }
  ParticlePool.prototype.add = function (x, y, dx, dy) {
    particles[firstFree].initialize(x, y, dx, dy);
    // handle circular queue
    firstFree++;
    if (firstFree == particles.length) firstFree = 0;
    if (firstActive == firstFree) firstActive++;
    if (firstActive == particles.length) firstActive = 0;
  };
  ParticlePool.prototype.update = function (deltaTime) {
    var i;
    // update active particles
    if (firstActive < firstFree) {
      for (i = firstActive; i < firstFree; i++) particles[i].update(deltaTime);
    }
    if (firstFree < firstActive) {
      for (i = firstActive; i < particles.length; i++)
        particles[i].update(deltaTime);
      for (i = 0; i < firstFree; i++) particles[i].update(deltaTime);
    }
    // remove inactive particles
    while (particles[firstActive].age >= duration && firstActive != firstFree) {
      firstActive++;
      if (firstActive == particles.length) firstActive = 0;
    }
  };
  ParticlePool.prototype.draw = function (context, image) {
    // draw active particles
    if (firstActive < firstFree) {
      for (i = firstActive; i < firstFree; i++)
        particles[i].draw(context, image);
    }
    if (firstFree < firstActive) {
      for (i = firstActive; i < particles.length; i++)
        particles[i].draw(context, image);
      for (i = 0; i < firstFree; i++) particles[i].draw(context, image);
    }
  };
  return ParticlePool;
})();

/**
 * 
 * @param {*} canvas 
 * 李峋爱心 canvas 元素
 * document.getElementById('pinkboard')
 * 
 * @param {*} heartColor 
 * 爱心的颜色
 * 默认为 #ea80b0
 */
function renderLxHeart(canvas, heartColor) {
  var context = canvas.getContext('2d'),
    particles = new ParticlePool(settings.particles.length),
    particleRate = settings.particles.length / settings.particles.duration, // particles/sec
    time;
  // get point on heart with -PI <= t <= PI
  function pointOnHeart(t) {
    return new Point(
      160 * Math.pow(Math.sin(t), 3),
      130 * Math.cos(t) -
        50 * Math.cos(2 * t) -
        20 * Math.cos(3 * t) -
        10 * Math.cos(4 * t) +
        25
    );
  }

  // creating the particle image using a dummy canvas

  var image = (function () {
    var canvas = document.createElement('canvas'),
      context = canvas.getContext('2d');
    canvas.width = settings.particles.size;
    canvas.height = settings.particles.size;
    // helper function to create the path
    function to(t) {
      var point = pointOnHeart(t);
      point.x =
        settings.particles.size / 2 + (point.x * settings.particles.size) / 350;
      point.y =
        settings.particles.size / 2 - (point.y * settings.particles.size) / 350;
      return point;
    }
    // create the path
    context.beginPath();
    var t = -Math.PI;
    var point = to(t);
    context.moveTo(point.x, point.y);
    while (t < Math.PI) {
      t += 0.01; // baby steps!
      point = to(t);
      context.lineTo(point.x, point.y);
    }
    context.closePath();
    // create the heart fill
    // '#ff30c5' '#ea80b0'
    context.fillStyle = heartColor || '#ea80b0';
    context.fill();
    // create the image
    var image = new Image();
    image.src = canvas.toDataURL();
    return image;
  })();
  // render that thing!
  function render() {
    // next animation frame
    requestAnimationFrame(render);
    // update time
    var newTime = new Date().getTime() / 1000,
      deltaTime = newTime - (time || newTime);
    time = newTime;
    // clear canvas
    context.clearRect(0, 0, canvas.width, canvas.height);
    // create new particles
    var amount = particleRate * deltaTime;
    for (var i = 0; i < amount; i++) {
      var pos = pointOnHeart(Math.PI - 2 * Math.PI * Math.random());
      var dir = pos.clone().length(settings.particles.velocity);
      particles.add(
        canvas.width / 2 + pos.x,
        canvas.height / 2 - pos.y,
        dir.x,
        -dir.y
      );
    }
    // update and draw particles
    particles.update(deltaTime);
    particles.draw(context, image);
  }
  // handle (re-)sizing of the canvas
  function onResize() {
    canvas.width = canvas.clientWidth;
    canvas.height = canvas.clientHeight;
  }
  window.onresize = onResize;
  // delay rendering bootstrap
  setTimeout(function () {
    onResize();
    render();
  }, 10);
}
